Refining of nonferrous metals



Patented July 9,1946

UNITED STATES PATENT oarce A REFINING 0F NONFERROUS DIE'IALS Louis s. Deltz, Jr; wesmelan. 3., asalgnor to Nassau smelting &'Befining Company, Incorporated, New York, N. Y., a corporation of New York llo Drawing.

This invention relates to the refining of non-' bearings, refinery and foundry scrap and materials from various other sources.

Application August 31, 1939. Serial No. 292.873

9 Claims. (01. 204-123) v These anodes may be electrolyzed in a bath I having substantially the following composition:

One object of the present invention is to provide an improved process for recovering the valu-. able constituents of such materials, and particularly to efiect a separation of tin and lead from the other constituents of these materials in substantially uncontaminated state.

One method embodying the invention may be a procedure which includes the steps of casting crude anodes from the scrap material. to which has been added sufiicient aluminum so that the cast anodes will contain aluminum in amounts not exceeding 1%, and electrolyzlng these anodes in an electrolyte having an acid, preferably one of the aromatic sulphonicacids; such as phenolsulphonic acid or benzene disulphonic acid, as its principal active electrolytic agent, to produce cathodes of substantially pure tin-lead alloy,

Other objects and features of the invention will appear from the following detailed description of one embodiment thereof in a process of the na ture described.

To illustrate a procedure embodying the invention and its advantages and which is applicable to the recovery of tin and lead primarily as pure solder and secondarily as Babbitt metal. let it be assumed that a'mass of white metal scrap of a type common at present in the'commercial market has been cast as received into crude anodes and that the material has substantially the following composition:

Anodes A Pounds Per cent per ton Tin. 84. 6 l, 692 Land I 9. 7 194 Antimony 3.5 70 Copper 1 2. l 42 Aluminum Q0 0 l G. p r liter Tin 15-25 Lead 10-15 Phenol sulphonic acid:

(calculated as total acid) 250-300 or (calculated as free acid) 200-250 A convenient way of making up this bath is to dissolve the required amounts of tin and lead salts of phenol sulphonic acid in water together with the required amount of free phenol sulphonic acid. The electrolysis is then preferably carried out at temperatures ranging from'SO C. to 70 C. and with a current density of eight to sixteen amperes per square foot.

The above describedelectrolysis would produce from 2000 lbs. of crude anodes about 1715 lbs. of solder cathodes and about 270 lbs. of shade slimes having substantially the following compositions:

cathodes A (1715 lbs.)

Per cent The above outlined process is a typical example of prior art procedure and results, given here only that a comparison may be made with the results of treating an almost identically similar material in accordance with the method of the invention. as follows:

In one instance a batch of similar material was melted, a suitable quantity of aluminum was added thereto, and crude anodes were cast from the resulting material. These anodes showed the following composition on analysis:

Anode: a moo tin.)

Pounds Per cent per ton Tin. 84. 4 I 088 9. 5 190 Antimony 3. 5 70 Copper 2. l 42 Alum 0. 6 10 Two thousand pounds of these anodes electrolyzed in the same bath and under the same conditions as described for Anodes A would produce about 1770 lbs. of solder cathodes and about 230 lbs. of anode slimes having substantially the fol lowing compositions:

cathodes B (1770 lbs.)

Per cent Pounds anodes were electrolyzed as described above, with the following results calculated to a base quantity of 2000 lbs.:

Anode: D (2000 lbs.)

Per cent Pounds sna Cathode: D (1818 the.)

Per cent Pounds Antimony (less than) 0.03 Copper (lem tban)- 0.03 7 Aluminum 0.00

Slimes D {s was Tin G9. 4 1, 682 Hall 10. T 180 Antimony 0. 03 Copper 0. 03

Alum 1 0. 00

Slimes B (230 lbs.)

Percent Pounds Anode: C (2000 lbs.)

Per cent Pounds When electrolyzed as above described. 2000 lbs. of these anodes would yield about 1794 lbs. of solder and about 206 lbs. of slimes showing substantially the following compositions:

cathodes c (m. lbs.)

' Per cent Pounds Slime: C (208 118.)

Per cent Pounds A similar material was melted, was

added thereto in accordance with the'invention,

crude anodes were cast therefrom. and these Per cent Pounds 40. 8 62 0. 6 l 39. 6 60 10. 1 l6 2. 7 i

A principal characterizing feature of the invention as illustrated in the above described procedure is the addition of aluminum to the raw material in such amount that the anodes cast from the raw material will contain aluminum in amounts not suintantially exceeding 1%. A suitable and satisfactory method of adding the aluminum is by stirring into the molten crude solder mixture such a quantity of an aluminum-tin alloy prepared for the purpose, e. g. an alloy of aluminum and 75% tin, as will introduce the requisite quantity of aluminum into the melt. The aluminum-tin alloy thus added to the melt may be introduced in either solid or in molten condition and should be thoroughly stirred in.

The aluminum can, of course, be added as pure metallic aluminum if desired.

In accordance with the present invention it has been discovered that the addition of aluminum in amounts not exceeding about 1% to crude anodes containing principally tin and lead with admixtures o! antimony and/or copper. as well as minor contaminations of other metals. results in notably diminishing the amount of tin contained in the anode slimee.

Thus, in the illustrative examples of the invention given above, the anode slimes A contain 147 lbs. of the 1692 lbs. of tin originally in the anodes. or 8.7%; whereas the anode slimes B contain 09 lbs. of the 1688 lbs. of tin originally in the anodes. or 6.9%. Again, the C slimes contain 7.2% and the D slimes 3.7% of the tin originally present. Hence. by comparing A with B and C with D it is clear that, in the first case. the addition of aluminum cuts down the proportion of tin in the slimes by over and in the latter case by over 48%. or nearly one half.

It is found that. where antimony is present in crude anodes of the general nature described, which are electroLvaed as dwcribed, substantially all of the antimony is found in the slimes and that theslimeswillcontainfromtwotothree times as much :tin as antimony; but if aluminum "in'"'amountsot the order of 1% or less be embodied in the crude anodes, all oi the antimony mony in the slimes are respectively 2.1 and 2.0,

whereas in B and D these ratios'are respectively 1.6 and 1.0. It is also found that a similar efiect is produced by aluminum when copper is present, which latter also tends to drag tin into the slimes.

Furthermore, the character or what is here termed anode slimes is worth noting. Generally speaking, whether aluminum is present in these anodes or not, Very little material actually falls 1 irom the anodes. A practically exhausted anode removed from the bath has substantially its original shape and overall dimensions. It consists of a thin central fin oi the original metal un altered. while the rest of its volume consists of a spongy mass from which has been dissolved the tin and lead now deposited on the cathodes.

It is thought that antimony and copper particularly and perhaps other metals present in relatively unimportant amounts, such as arsenic, perhaps, or iron, or zinc, form with the preponderant tin intermolecular compounds in crystalline spongy networks between the preponderantly present lead, tin and lead-tin crystals. These tinantimony, tin-copper, perhaps tin-'antimony-copper quasi compounds do not dissolve in the bath.

The tin, lead and possible lead-tin crystals are dissolved, leaving the impurities as an insoluble metallic sponge. It is thi sponge which is herein termed anode slimes forwant oi a better designation.

; metallic mixtures containing a substantial quan' principally of tin and lead and containing a minor quantity of metal of the group consisting of copper and antimony, which comprises incorporating such a quantity of aluminum in said metal as to constitute from about 0.2% to about 0.5% of the resulting alloy, and eleotrolyzing anodes oi the resulting aluminum-bearing alloy in an electrolyte'whose principal electrolytic agent is an aromatic sulphonic acid to cathodically deposit a substantially pure tin-lead alloy, .the aluminum being present in the anodes in an amount sunlcient to prevent the occurrence in the anode slimes of a material quantity of tin which would otherwisebe precipitated in said slimes.

2. The process of refining metal consisting principally of tin and lead and containing a minor quantity of antimony, which comprises incorporating in said metal a quantity of aluminum not exceeding about 1% of the weight of said metal, and electrolyzing anodes of the resulting aluminum-bearing metal in an electrolyte whose principal electrolytic agent is an aromatic sulphonic acid to cathodically deposit a substantially pure tin-lead alloy. the aluminum in the anodes acting to prevent the occurrence in the anode slimes of a material quantity of tin which would otherwise be precipitated in said slimes.

3. The method of separating tin and lead from tity'of lead, a relatively large amount of tin and a minor quantity of antimony, which comprises incorporating aluminum in such a mixture to the extent of not more than about 1%, and electrolysing anodes of the resulting aluminum-bearing n: is thought further that when aluminumis added to these crude solders in the manner described, the aluminum displaces the tin at least in part from the intermolecular compounds with antimony and copper and perhaps also inhibits otherwise the entry of tin into such compounds,

' tending to force tin to remain in a soluble state.

This seems the more probable since it is found that the aluminum itself does not dissolve appreciably in the electrolyte but is substantially entirely found in the anode slimes. Thus, the

aluminum has distinct and definite advantages and appears to present no objectionable-properties in the procedure It is also found that theanode slimes described are generally metallic in character as formed; and, hence, these slimes do not tend to bar the passage of the electric current or to tame the required voltage up to excessivelycostlyvalues.

' The slimes when dried and crushed in the air tend to oxidize spontaneously more or less. Hence, the percentages in the above of the various slimes do not total 100%, the difference-being 7 probably chiefly oxygen. From the foregoing it will be apparent that the invention provides a; simple, eflective and economical improved procedure for refining nonferrous metals and in particular for recovering tin or lead or both from materials containing eitherv or both of these metals with admixtures oi antimony or copper or both and other impurities. Various modifications and changesi'rnay, of course, he made to adapt the invention to varying conditions. Hence, the invention is not limited to the specific embodiment described herein butembraces all modifications and equivalents falling within the scope of the appended claims,

What is claimed is:

1. Zihe process or refining. metal consist-lasts mixture in an electrolytic cell comprising electrolyte whose principal electrolytic agent is a sulphonic acid of the group consisting of phenol sulphonio acid and benzene disulphonic acid, whereby a substantially pure alloy of lead and tin is deposited at the cathode of said cell and the aluminum prevents the occurrence in the anode slimes of a material quantity of tin which wouldv extent of not more than about 1%, and electroly'zing anodes of the resulting aluminum-bearing mixture in an electrolytic cell comprising an electrolyte whose principal electrolytic agent is phenol sulphonic'acid, whereby a substantially pure alloy or lead and tin is deposited at the cathode oi said cell and the aluminum prevents the occurrence in the anode slimes of a material quantity oi tin which would otherwise be precipitated in 7 said slimes.

5. The method of separating tin and lead from metallic mixtures containing a, substantial quantity of lead, a relatively large amount of tin and a minor uuantityof antimony, which comprises incorporating aluminum in such a mixture to the extent of not more than about 1%. and electrolymng anodes of the resulting aluminum-bearing mixture in an electrolytic cell comprising anelec-' trolyte whose principal electrolytic agent is henzene disulphonic. acid, whereby a substantially quantity oi'tin which would otherwise ciiiitatedinsaid slimes.

pure alloy of'lead and tin is deposited at the cathode'oi said cell and the aluminum prevents theoccurrence in the anode slimes of a material 8. The process 01 refining metal co principally oitin and lead and con 'amlnor quantity oi antimony, which comprises incorporating in said metal a quantity of aluminum not exceeding about 1% of the weight of said metal, and electrolyzing anodes of the resulting aluminum-bearlng metal in an electrolyte containing from about 250 to about 300 grams per litre of phenol sulphonic acid calculated as total acid, whereby a substantially pure tin-lead alloy is cathodicaliy deposited and the aluminum in the anodes acts to prevent the occurrence in the anode slimes of a material quantit of tin which would otherwise be precipitated in said slimes.

'1. The process of refining metal consisting principally of tin and lead and containing a minor quantity of antimony, which comprises incorporating in said metal a quantity of aluminum not exceeding about 1% of the weight of said metal, and electrolyzing anodes o! the resulting aluminum-bearing metal in an electrolyte containing from about 200 to about 250 grams per litre of free phenol sulphonic acid and from about 250 to about 300 grams per litre of phenol sulphonic acid calculated as total acid, whereby a substantially pure alloy of lead and tin is cathodically deposited and the aluminum prevents the occurrence in the anode slimes of a material quantity of tin which would otherwise be precipitated in said slimes.

8. The process of refining metal consisting principally of tin and lead and containing minor tially pure tin-lead alloy, the aluminum in the anodes acting to prevent the occurrence in the anode siimes oi a material quantity of tin which would otherwise be precipitated in said slimes;

9. The method of separating tin and lead from metallic mixtures containing a substantial quantity oi lead, a relatively larg amount of tin and minor quantities or antimony and copper, which comprises incorporating aluminum in such a mixture to the extent oi'not more than about 1%, and electrolyzing anodes oi the resulting aluminum-bearing mixture in an electrolytic cell comprising an electrolyte whoseprincipal electrolytic agent is a sulphonic acid selected irom the class consisting of phenol sulphonic acidand benzene disulphonio acid, whereby a substantially pure alloy of lead and tin is deposited at the cathode of said cell and the aluminum prevents the occurrence in the anode slimes of a material quantity of tin which would otherwise be precipitated in said slimes.

LOUIS S. DEI'IZ, JR. 

